D1.3 oncept Description - endlessrunway-project.eu · D-GPS Differential Global Positioning System DLR Deutsches Zentrum für Luft- und Raumfahrt EASA European Aviation Safety Agency

D1.3 Concept Description High-level overview

This document contains the high level operational concept for operating the Endless Runway. A

number of design elements will be defined, based on the division in airport design, aircraft

characteristics, and ATM procedures. Each of the elements will be worked out in detail in a number

of requirements, which all will be further analysed.

Project Number 308292

Document Identification D1.3_WP1_Concept_Description

Status Final

Version 2.0

Date of Issue 21-12-2012

Authors NLR, ONERA, DLR, INTA

Classification Public

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Ref.: D1.3_WP1_Concept_Description

Status: Final version 2.0

Date: 21-12-2012

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The Endless Runway D1.3_WP1_Concept_Description

Document Change Log

Version Author Date Affected Sections Description of Change

0.1 H. Hesselink

S. Aubry

7/10/2012 All Initiation of the document

structure

0.2 M. Dupeyrat

P. Schmollgruber

S. Loth

R. Verbeek

A. Remiro

M. Vega Ramírez

27/11/2012 All

Addition of requirements,

analysis and use cases

1.0 H. Hesselink 30/11/2012 All Release version

1.1 M. Dupeyrat 7/12/2012 All Review of the document

1.2 C. Welman 18/12/2012 All Review of document

2.0 H. Hesselink 21/12/2012 All New release

Document Distribution

Organisation Name

EC Ivan Konaktchiev

NLR Henk Hesselink, René Verbeek, Carl Welman, Joyce Nibourg

DLR Steffen Loth

ONERA Maud Dupeyrat, Sébastien Aubry, Peter Schmollgruber

INTA Francisco Mugnoz Sanz, María Vega Ramírez, Albert Remiro

ILOT Marián Jez

Review and Approval of the Document

Organisation Responsible for Review Reference of comment documents Date

All 1.0 21-12-2012

Organisation Responsible for Approval Name of person approving the document Date

NLR H. Hesselink 21-12-2012

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Table of Contents

Document Change Log 2

Document Distribution 2

Review and Approval of the Document 2

Abbreviations 5

Introduction 7 1.

1.1 Description of the Endless Runway 7

1.2 Operating the Endless Runway 8

1.3 Document contents 9

Identification of design elements 9 2.

Requirements for the design of the Endless Runway 11 3.

3.1 Methodology 11

3.4 ATM procedures 18

3.4.1 Runway Operations 18

3.4.2 Paths/Routing (Departure/Arrival) 19

3.4.3 Determination of take-off/touchdown points by ATC 19

3.4.4 Missed approach procedures 20

3.4.5 Navigation aids 20

3.4.6 Separation 20

3.4.7 Situational awareness for air traffic controllers 21

3.4.8 Handle different meteorological conditions 21

3.4.9 Environmental aspects 22

Analysis 22 4.

4.1 Methodology 23

4.3 Aircraft aspects 36

4.3.1 Passenger comfort 36

4.3.2 Take-off and landing parameters 39

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4.3.3 Landing gear 43

4.3.4 Engines 44

4.3.5 Aircraft ground clearances 45

4.3.6 Situational awareness for the pilot 47

4.4 ATM procedures 48

4.4.1 Runway Operations 48

4.4.2 Paths/Routing(Departure/Arrival) 55

4.4.3 Determination of take-off/touchdown points by ATC 59

4.4.4 Missed approach procedures 61

4.4.5 Navigation aids 62

4.4.6 Separation 63

4.4.7 Situational awareness for air traffic controllers 66

4.4.8 Handle different meteorological conditions 67

4.4.9 Environmental aspects 71

Use Cases 71 5.

5.1 Emergency stop on the banked part of the runway 71

5.2 Emergency landing 72

5.2.1 Malfunction of landing gear deployment 72

5.2.2 Aircraft banking not possible before landing 72

5.2.3 Touchdown point not reached 72

5.3 Different shapes 73

Conclusion 75 6.

References 75 7.

Appendix A. Definition of gates 76

Appendix B. Automated People Movers 80

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Abbreviations

Acronym Definition

4D 4-Dimensional

A Area

ACARE Advisory Council for Aviation Research and Innovation in Europe

APM Automated People Mover

ATC Air Traffic Control

ATM Air Traffic Management

ATO Automatic Train Operation

ATP Automatic Train Protection

ATS Automatic Train Supervision

D-GPS Differential Global Positioning System

DLR Deutsches Zentrum für Luft- und Raumfahrt

EASA European Aviation Safety Agency

FAA Federal Aviation Administration

ft feet

FMS Flight Management System

H hour

HUD Head Up Display

ICAO International Civil Aviation Organisation

ILS Instrument Landing System

ILOT Instytut Lotnictwa

INT International

INTA Instituto Nacional de Técnica Aeroespacial

Km kilometre

m meter

MLS Microwave Landing System

NAT National

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NLR Nationaal Lucht- en Ruimtevaartlaboratorium

NM Nautical Mile

OEI One Engine Inoperative

OFZ Obstacle Free Zone

ONERA Office National d’Études et de Recherches Aérospatiales

pph per passenger hour

REQ Requirement

RVR Runway Visual Range

s second

SESAR Single European Sky ATM Research

TMA Terminal Manoeuvring Area

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Introduction 1.

As was identified by ACARE, the Advisory Council for Aeronautics Research in Europe, the lack of capacity at

airports is a major constraint to growth in air transport today and in the following decennia [1]. One of the

major challenges is to increase available airport capacity by optimizing the use of the existing runway system

throughput within the limits of safety, emissions and noise. Providing sustainable capacity of the runway

system under all meteorological conditions is another challenge.

A number of physical constraints, such as wake vortex separation minima and cross- and tailwind limits, make

it hard to improve the performance of conventional airport configurations in significant ways. Major reasons

for these capacity limitations are the imposed direction of the runway system and the need to have aircraft

operating along the same approach path to the same touchdown point. Directionality results in a dependency

to the wind direction and speed. Using the same approach path results in trailing aircraft having to avoid wake

vortices from leading aircraft.

The current activities in the scope of SESAR (Single European Sky ATM Research), although getting us closer to

the capacity levels needed with its advanced technologies, might not be sufficient to obtain the capacity

needed for an intended three-fold increase in air traffic, specifically under all weather conditions. This is why a

fundamentally new approach is proposed.

1.1 Description of the Endless Runway

A novel and radical concept is proposed here: the Endless Runway, a concept which consists of an airport with

one circular circumventing runway. This runway is used for take-off in any direction and landing from any

direction. The airport terminals with all aircraft, passenger, baggage and freight facilities are located mainly

inside the circular runway. This will allow aircraft to shorten their global trajectory through optimized

departure and arrival routes, and will offer the unique characteristic that the runway can be used under any

wind condition through the possibility for an aircraft to operate always with headwind during take-off and

landing. Moreover, runway crossings are avoided and runway overruns cannot occur since the runway has no

end.

The circle of the runway will need to be large enough to provide sufficient room for infrastructure preferably

inside the circle. Therefore, it will have a radius of 1.5 to 2.5 kilometres. This magnitude should allow current-

day aircraft to use the circle without significant structural modifications.

The Design of The Endless Runway consists of a banked circular runway with all facilities for aircraft, passenger,

baggage, and freight handling being located inside the circular runway, so that passenger fast transfer times

and small taxiing distances can be achieved.

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1.2 Operating the Endless Runway

Wind direction, wind speed, and visibility conditions are the major factors in the decision of air traffic control

to use a certain runway configuration. Limits on tailwind and crosswind components determine whether

runways can be used or not, and low visibility limits the use of dependent runways. The fixed direction of the

runways results in a dependency to the wind direction, and to the fact that following aircraft must use the

same approach path, resulting in the need for wake turbulence separation. The Endless Runway operates a

concept consisting of a circular runway that allows take-off in any direction and landing from any direction,

avoiding the constraints mentioned before.

Three different situations can be identified for aircraft landing on the circular runway: strong wind, low wind,

and changing wind directions.

a) In strong wind conditions, the aircraft will fly in sequence towards the Endless Runway to allow for

landing at the touchdown point where dependency from the wind is at a minimum (at exactly

headwind). This is not different from today, with the exception that an optimum touchdown point

always exists whereas for a conventional runway a certain crosswind needs to be accepted.

b) In low wind conditions, aircraft can land towards any direction. Aircraft are sequenced so that

consecutive aircraft originate from different directions and do not have to be spaced according to

wake turbulence categories. This enables the possibility for shorter landing intervals (see Figure 1).

.

Figure 1 Flexible sequencing of aircraft on the Endless Runway

c) With changing wind, the aircraft sequence can gradually “move” with the wind direction. No break in

the sequence occurs as it can occur with conventional runway configurations. No costly operation for

tactical runway changes or runway directions change in operation is necessary.

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From a capacity point of view, the Endless Runway seems to be advantageous compared with a classical

runway system. It reaches a sustainable maximum capacity under every wind condition with every wind

direction. The Endless Runway project will assess capacity of the newly proposed runway, but also take into

consideration the additional developments it involves (ATC new tools and procedures), and the trade-offs

(from an environmental standpoint, etc.).

1.3 Document contents

This document contains the high-level operational concept for the Endless Runway, divided in three distinct

parts and based on the high-level requirement that was set in the work plan [2] for this task:

Req. 1 The WP shall propose one or more operational concepts to apply for the use of the Endless

Runway. The concepts will consider ATM elements, airport infrastructure, and aircraft

aspects.

The document describes the concept of operation of the Endless Runway. However, where certain decisions

cannot be made yet, the concept description will leave different options to be studied further in the following

work packages. Just as well, it may be possible that more than one concept can be applied to operating the

circular runway, in which case each concept will be described separately. An example of more than one

concept is already given in the description above, concerning high wind and low wind conditions..

The document first presents a list of high-level design elements, which all need to be considered to get the

operational concept picture. This list is presented in chapter 2. Each of the design elements is then elaborated

in one or more requirement in chapter 3.

In chapter 4, an analysis of the requirements is made, based on the description of the state-of-the-art on

runway operations [3] and a brainstorm session that was held within the consortium. Use cases provided in

chapter 5 complete the whole picture by describing non-nominal situations that need to be considered.

Identification of design elements 2.

Many aspects play a role in the design of operations for the Endless Runway. The state-of-the-art document for

the Endless Runway [3] describes the basic principles of current airport design, aircraft characteristics, and

ATM procedures, in relation to aircraft operations on circular runway tracks and related airport design. The

document also provides an overview of related past and current circular runway initiatives.

To identify relevant aspects and to find first solutions, a workshop was organised with experts on airport

design, environmental procedures, and a pilot. The workshop resulted in an identification of aspects that will

need to be considered for the construction of an operational concept for the Endless Runway.

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Both the state-of-the-art document and the results of the expert’s workshop form the basis for this document:

the concept description of the Endless Runway.

The following design elements are considered relevant for the high-level concept, subdivided in the three

topics that will be further elaborated in the project:

For airport design:

Size of the circle (circle radius and runway width)

The runway profile curvature (bank angles)

The layout of taxiways and aprons

The location of the control tower

Terminal buildings, hangars, maintenance area, fire building, etc.

Access to the airport

For aircraft characteristics:

Passenger comfort

Take-off and landing parameters

o Speed

o Bank angle

o Identification of best take-off and landing point

Landing gear

Engines

Aircraft ground clearance

Situational awareness of the pilot

For ATM procedures:

Runway operations

Paths and routing (departure/arrival/curved approaches)

Take-off/touchdown point determination

Missed approach procedures

Navigation aids

Necessary separation

Situational awareness of air traffic controllers

Different meteorological conditions handling (strong wind, low wind)

Environmental aspects (avoid communities – noise, air pollution, noise, third-party risk)

Several of the identified elements are interrelated so that decisions will influence more than one element.

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For some of the elements it will not be possible to make one final decision yet, so that options will be left

open. The decision may depend on the actual operation that is expected, for example: the size of the circle will

depend on the required capacity and the expected traffic mix. In other occasions, the decision may depend on

operational conditions while operating the Endless Runway, for example: two different situations exist,

depending on the wind speed, which will determine whether aircraft will have to land headwind all at the

same touchdown point or whether the aircraft can land anywhere in the circle.

Existing aviation regulatory framework and constraints need to be considered as well, knowing that some

aspects of existing airport operations will not be applicable any longer or will need a considerable change at

the 2050 horizon.

This document will elaborate on the above mentioned design elements through the identification of related

requirements followed by an analysis of these requirements.

Requirements for the design of the Endless Runway 3.

This chapter provides requirements on the design of the Endless Runway, based on the design elements

described in chapter 2. This chapter is organised along the same streams as the project: first, requirements on

the airport design will be given, then those on the aircraft characteristics, and finally on ATM procedures.

The requirements are derived from the state-of-the-art document [3], where each section concluded with a

discussion on the relation between the topic and the Endless Runway.

3.1 Methodology

Requirements based on the list of design elements will be elaborated through a brief description of the design

element and the identification of one or more requirements. Requirements are numbered.

Each requirement contains:

“shall”, to indicate a mandatory requirement, or

“should”, to indicate a requirement that is preferably taken into consideration.

When an explanation is given in the text following the requirement, the words “must” or “will” shall be used to

indicate a new formulation of the requirement or additional information.

3.2 Airport design

The airport design concerns all the elements related to the construction of the runway and the layout of

airport infrastructure (taxiways, aprons, and building). This section will also give requirements for access to the

airport.

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Each requirement will be identified with the designator “DESIGN” and a sequence number.

3.2.1 Size of the circle

Requirements on the size of the circle are concerned with the radius of the circle and the width of the runway.

The length of the runway is determined taking into consideration the aircraft ground roll for the expected

traffic mix (see aircraft performance in section 3.3) even in degraded meteorological conditions, and, on the

ATM side, the simultaneous number of operations on the runway and the separation requirements imposed by

the ATM system.

REQ-DESIGN-01 The runway circle shall allow a sufficient number of operations for the following

types of airports: • Seasonal non-hub airports, including a mix of aircraft where mid-size aircraft are

predominant. • Large, non-seasonal hub airports with a strong home carrier that operates mostly large

aircraft. • Large airports with a mix of aircraft, including mid-size and large aircraft.

In order to provide flexibility, specific traffic numbers will be avoided. Ranges for capacity

figures will be used instead.

REQ-DESIGN-02 The runway circle shall offer sufficient space for the most important airport facilities

to be constructed inside the circle.

Airport facilities must be capable of handling the assigned number of aircraft and serve the

airport’s purpose (e.g., a hub airport will require fast and efficient transfer of passengers). The

most important facilities include as a minimum the terminal buildings and baggage facilities,

which must be located inside the circle. This will permit to design a more compact airport.

REQ-DESIGN-03 The runway circle should offer sufficient space for other airport facilities to be

constructed inside the circle.

Other airport facilities include all infrastructures for aircraft parking and maintenance, like

hangars and maintenance areas.

3.2.2 Bank angle

Requirements on the runway transversal profile deal with the use of a bank angle by aircraft while taking off,

landing, and taxiing on the runway. A means for crossing the runway from inside to outside the circle and vice

versa for aircraft and other vehicles must be available.

The bank angle will make the aircraft accelerate towards the higher part of the runway during take-off and

decelerate towards its lower part during landing. Wingtip and engine clearance with the ground must be

guaranteed at all time for all aircraft types.

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REQ-DESIGN-04 The runway, with a given radius, shall have a gradually increasing bank angle

allowing take-off and landing speeds for the aircraft intending to operate on the runway.

The runway curvature must comply with this bank angles range, which depend on the aircraft

take-off and landing speeds. Typical take-off and landing speeds are given in the following

table:

Aircraft type Aircraft description ICAO

code

Engine

type

Take-off

speed (kts)

Landing

speed (kts)

Large Airbus 380-800 A388 Jet 150 156

Mid-sized Airbus A320-232 A322 Jet 151 137

Regional Saab SF340B SF34 Turboprop 128 105

Business jet Dassault Falcon 20 FA20 Jet 138 129

Military bomber Rockwell B-1 Lancer B1 Jet 250 220

General aviation Diamond DA 40 DA40 Jet 54-67 58-73

REQ-DESIGN-05 The bank angle of the runway shall consider engine clearance, wingtip clearance,

and the tip-back angle (during take-off rotation) of the aircraft.

The following table shows wingtip heights of various aircraft on a flat track:

Aircraft type Aircraft description ICAO code Wingtips height (m)

Large Airbus A380-800 A388 5.3

Mid-sized Airbus A320-232 A322 3.7

Regional Saab SF340B SF34 2.5

Business jet Dassault Falcon 20 FA20 1.5

Military bomber Rockwell B-1 Lancer B1 3.6

General aviation Diamond DA 40 DA40 0.73

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The difficulty resides in the curvature of the runway (e.g., polynomial shape) that reduces the

distance between the external wing elements (wingtips, engines) and the ground.

REQ-DESIGN-06 The link between the taxiways and the runway shall not contain abrupt transitions.

This applies on both sides of the runway, towards the inside and the outside of the circle.

3.2.3 The layout of taxiways and aprons

Requirements on the layout of taxiways and apron concern the design and number of the taxiways to get from

the apron to the runway and vice versa. They include assertions on high speed runway exits and entries to the

runway including runway entry buffers. The apron must provide easy access and cater for push back without

disturbing traffic flows. Room for other traffic must be available.

REQ-DESIGN-07 High-speed exits should be available to minimise runway occupancy times of

arriving aircraft.

REQ-DESIGN-08 High-speed entries should be available to minimise runway occupancy times of

departing aircraft.

In contrast to conventional runways that are used in segregated mode (i.e., landing only or

take-off only), aircraft waiting on the Endless Runway before taking-off, occupy a significant

part of runway and prevent other aircraft from landing or taking-off behind these waiting

aircraft.

REQ-DESIGN-09 Runway holding areas shall be designed.

The runway holding areas must allow for a number of aircraft to wait behind each other for

take-off. The size of the holding areas will depend on the number of runway entries and the

need for consecutive aircraft to use the same entry. This will follow from the design decisions

and from simulations.

REQ-DESIGN-10 Taxiways shall be designed in a way to minimize the distance between the runway

and the apron.

3.2.4 The location of the control tower

Requirements for the control tower deal with the position from where a full view on the runway must be

possible, hence with the distance between the tower and the runway.

REQ-DESIGN-11 The control tower should be located somewhere near the centre of the circle in

order to have equal visibility towards all parts of the runway and the other parts of the airport

and be sufficiently high to allow a good view.

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3.2.5 Terminal buildings, hangars, maintenance area, fire building, etc.

Requirements for the terminal buildings include their locations inside the circle that must allow easy access for

aircraft on the airside, and for passengers and airport personnel on the landside. A minimum list of support

buildings (like the fire station) must be defined.

REQ-DESIGN-12 Terminal buildings shall be constructed such that they will fit the purpose of the

airports: hub airport or point-to-point airport.

The number of (transfer) passenger must be considered in the terminal design.

REQ-DESIGN-13 (Connected) gates and aircraft parking positions shall be located at the airport in

such a way that taxiing distances and times are minimised.

A constraint on the location of the gates may be that airlines, in particular a home carrier or a

hub airline, will prefer to have their gates located close to each other.

REQ-DESIGN-14 The number of gates at the airport shall be sufficient for the intended use of the

airport (see also REQ-DESIGN-01).

To define the necessary number of gates, various turnaround times for the expected traffic

mix must be considered, just as the fact that aircraft may need to wait a certain time after

de-boarding and before boarding begins, depending on the airline’s schedule.

REQ-DESIGN-15 Airport stakeholders’ needs shall be taken into account.

Passengers, airlines, owners and commercial services influence the configuration of terminal

areas. Usually it is impossible to define a configuration which suits all of them. Priorities must

be established.

REQ-DESIGN-16 Hybrid configurations (consisting of a mixture of centralized and decentralized

facilities) should be adopted in order to provide operational flexibility.

3.2.6 Access to the airport

Requirements for access to the airport contain the specific necessity for passengers and personnel to access

the terminal buildings. Obviously, with an impassable circular runway, a way to get inside the circle must be

found. These requirements include transportation means to get to the airport.

REQ-DESIGN-17 Curb-side roadways should be located so that no additional land area is required

inside the circle.

REQ-DESIGN-18 Automated People Mover vehicles should be used in order to ease users transport

inside the Endless Runway.

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REQ-DESIGN-19 In order to satisfy users’ needs (originating and terminating travellers, employees,

supply, delivery and other commercial services), the airport shall provide high-speed, reliable

and economic access routes.

Underground routes under the airport (airside and landside) or personal aircraft (PPlane

concept) are options for transporting people around the airport.

3.3 Aircraft aspects

The aircraft characteristics concern the requirements that the aircraft have to match to enable their operation

on the Endless Runway. They are mainly related to the aircraft take-off and landing phases.

Each requirement is identified with the designator “AIRCRAFT” and a sequence number.

3.3.1 Passenger comfort

A specific requirement on passenger comfort is needed to assess the perception of passengers when taking-off

from and landing on the Endless Runway.

REQ-AIRCRAFT-01 The endured acceleration during the curved ground roll at take-off and landing

shall not exceed sustainable values for passengers’ safety and comfort.

For instance, trains are designed so that passengers do not sustain a lateral acceleration higher

than 1.2 m/s2, which corresponds to 0.23 g. This value can be used as an initial reference for our

aircraft study. The main difference is that in the case of the Endless Runway, not only the aircraft

direction but also its speed varies. This part of the acceleration (longitudinal acceleration) needs

to be considered as well.

3.3.2 Take-off and landing parameters

The Endless Runway concept implies additional requirements on take-off landing parameters (take-off and

landing location, speed, acceleration, and bank angle) in comparison to today’s operations on straight

runways.

REQ-AIRCRAFT-02 The take-off and landing speeds shall be within the maximum speed allowed by

the runway.

REQ-AIRCRAFT-03 The aircraft shall land at a precise point at a given speed and a given bank angle.

The location of the aircraft ground roll during landing and thus of the landing point is optimized

according to wind direction and speed.

REQ-AIRCRAFT-04 The aircraft shall take-off at a precise point at a given speed and a given bank

angle.

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The location of the aircraft ground roll during take-off and thus of the take-off point is optimized

according to wind direction and speed.

REQ-AIRCRAFT-05 Take-off and landing vertical slopes shall be high enough to avoid any contact

between the extended landing gears and the higher part of the runway when the aircraft is

airborne and overflying the runway.

3.3.3 Landing gear

Requirements on the landing gear are related to the structural strength of the landing gear that must allow the

aircraft to take-off from and land on a banked runway.

REQ-AIRCRAFT-06 The landing gear shall be able to withstand the loads generated during landing.

REQ-AIRCRAFT-07 The landing gear layout shall provide satisfactory stability during ground run

(take-off and landing).

3.3.4 Engines

The asymmetrical shape of the runway may impose requirements on engines size and power set-up.

REQ-AIRCRAFT-08 Engines forces should consider a ground run on a circular and therefore

non-symmetrical runway.

3.3.5 Aircraft ground clearances

The banked shape of the runway imposes requirements on the clearance between the aircraft and the ground.

REQ-AIRCRAFT-09 The tip-back angle of aircraft should be tailored to the runway transversal profile

to avoid ground contact during take-off rotation.

REQ-AIRCRAFT-10 The aircraft configuration shall ensure clearance between aircraft components

(e.g., wingtips and engines) and the banked runway.

3.3.6 Situational awareness for the pilot

In the 2050 context, it is assumed that the pilot will have any required information on the cockpit displays for

situational awareness, not only from the aircraft point of view (attitude, location, etc.), but also from the ATM

perspective (surrounding traffic and planned trajectories displayed for traffic collision avoidance). At one

point, he will have the opportunity to activate or refuse the automated take-off and landing sequence.

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REQ-AIRCRAFT-11 The flight crew shall receive the landing or take-off point in negotiation with ATC.

REQ-AIRCRAFT-12 The flight crew shall be able to follow the take-off and landing sequence thanks to

appropriate on-board navigation systems.

3.4 ATM procedures

Requirements on ATM procedures are concerned with the ATM aspects on ground and in the air and include

runway operations, procedures for arrival and departure routes, taxiway operations, controller’s situational

awareness, and decision support systems.

Each requirement is identified with the designator “ATM” and a sequence number.

3.4.1 Runway Operations

The following requirements are related to the general use of the runway resource to ensure safe and efficient

operation.

REQ-ATM-01 Simultaneous use of the runway shall be allowed.

With only one “physical” runway available, it must be allowed to operate more than one

movement at the same time on different parts of the runway in compliance with the defined

safety regulations.

REQ-ATM-02 Direction of operation should be flexible.

It must be possible to operate the runway clockwise and counter-clockwise to be adaptable

to the operational needs. This includes also opposite traffic operations (in strong wind

conditions).

REQ-ATM-03 4D operations shall be available.

4D-trajectory information must be available to allow efficient and safe use of the runway

resource.

REQ-ATM-04 Coordination support tools shall be available.

ATC should be supported in its activities of traffic coordination and runway allocation.

Because of the high complexity of these operations and the level of required planning,

system support must be available.

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3.4.2 Paths/Routing (Departure/Arrival)

Requirements on departure routes concern the definition of Standard Instrument Departures or similar

procedures for aircraft that take-off from the Endless Runway. Requirements on flying towards the runway are

also defined. The airspace around the airport must be used optimally, so that separation between consecutive

aircraft can be kept to a minimum. The approach paths will need to allow aircraft to make a bank angle just

before touchdown.

REQ-ATM-05 Airport taxi in/out routes shall be defined to allow the pilot to choose the most cost

effective route from the apron to the runway entry point and from runway exit to the gate.

The airport infrastructure of aprons and taxiways must enable short and efficient taxi routes. The

pilot, in negotiation with air traffic control, will have a strong influence on the choice of the most

efficient one.

REQ-ATM-06 Departure/arrival routes shall be defined that will allow the pilot to choose the most

cost effective route from the runway to the Terminal Manoeuvring Area (TMA) exit or from the

TMA entry to the touchdown point.

Short and efficient routes must be available for the pilot to fly towards the requested TMA exit

point or towards the touchdown point. Routes and exit points may be selected from a number of

predefined ones or can be made flexible, depending on the situation. It is assumed that the pilot

will have a strong influence on the choice of the route. In negotiation with air traffic control, a

route can be agreed.

3.4.3 Determination of take-off/touchdown points by ATC

Requirements on the take-off and touchdown points deal with where to define the take-off and touchdown

points’ location, the number of take-off and touchdown points and the possibility to use more than one

simultaneously. Furthermore, the relation between the start of the roll and the take-off point and between the

touchdown point and the end of roll will need to be defined.

REQ-ATM-07 ATC shall be able to determine the optimal take-off and touchdown points for each

individual aircraft, based on the aircraft trajectory, cross- and tailwind limits and other traffic.

Crosswind limits of in between 15 and 20 knots usually apply. It must be evaluated how the

aircraft operating on the Endless Runway will be affected by crosswind conditions; stricter

minima may be necessary.

Tailwind constraints for take-off and touchdown must be complied with. Maximum tailwind limits

of 10 knots usually apply. Tailwind operations require a longer take-off and landing run. This may

not be a problem on the Endless Runway since there is no runway end. However, it should be

avoided since it will reduce the runway space available for other aircraft. Another reason for

limiting tailwind operations is the higher relative speed difference between an aircraft

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taking-off/touching down and the air. The lower the relative speed, the safer the operations

become as the speed change between the ground roll and the airborne phase is minimised.

3.4.4 Missed approach procedures

Further to safety aspects, requirements must be defined on procedures to follow in case of go-arounds and for

touch-and-go on the runway. Missed approach procedures have to be defined with more flexibility than for

straight runways, as the touchdown point and the direction to continue the flight have to be defined for any

possible touchdown point.

REQ-ATM-08 A missed approach procedure strategically separated from the other traffic flows

shall be available.

The procedure must be simple to execute by the pilot, unambiguous, and feasible under low

visibility conditions.

3.4.5 Navigation aids

Requirements on navigation aids specify the equipment necessary to enable operating the aircraft on the

circular track.

REQ-ATM-09 Ground-based or space-based navigation aids shall be available to assist the pilot to

take off and land with high precision on any point defined on the circle in any visibility condition.

Navigation aids can be visual (only for good visibility conditions) or electronic means to assist the

aircraft in determining the exact point for taking off and landing on the circular runway track.

Navigation aids can be ground based, space based, or a mix of both and may rely on navigation

systems on board the aircraft.

REQ-ATM-10 Ground based or space based navigation aids shall be available to assist the pilot to

perform an Instrument Departure or Instrument Arrival from and towards the Endless Runway.

The navigation system must allow the aircraft to fly the departure and approach path as specified

in the following requirements, including the route to fly and manoeuvres to perform (e.g., roll

angle to match the necessary bank angle over the runway).

3.4.6 Separation

Requirements on separation will define the necessary distance between aircraft on the runway and on the

approach and departure routes towards the runway. One can imagine that through extending the curve on the

approach path, wake turbulence would be avoided and following aircraft could be separated with shorter

separation than today. The same applies for departing aircraft. Reduced separation could also be achieved

through the use of different runway touchdown points for consecutive aircraft. In the air, vertical, horizontal,

and lateral spacing can be applied.

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REQ-ATM-11 Departure routes should be strategically separated from approach routes.

Departure and approach routes will preferably not have common parts and will be separated so

that wake turbulence spacing is guaranteed, although an operational concept allowing the use of

the available airspace for departures and arrivals simultaneously might be thought of. Current

separation criteria will apply for aircraft following each other while using the same path. New

criteria may need to be defined for aircraft on different departure or approach routes. Current

separation requires 500 ft vertical and 1.3 NM lateral spacing.

REQ-ATM-12 Separation minima shall be applied for aircraft on the runway to avoid collisions.

A safety margin will need to be built in to ensure that an aborted take-off or a landing incident on

the runway will not lead to collisions with other traffic. ROT could be the limiting factor at the

end when it comes to high capacity operations.

3.4.7 Situational awareness for air traffic controllers

Requirements for the situational awareness for air traffic controllers concern the human machine interface

and the air traffic controllers’ processes to be able to understand the traffic situation at any time.

REQ-ATM-13 ATC shall have an adequate situational awareness of the operations around and on

the airport with the assistance of a suitable traffic monitoring system.

Especially when traffic is moving to and originating from different directions simultaneously, air

traffic control will be performed differently from today. Air traffic controllers will need to have a

level of situational awareness that will allow them to assess instantly whether a traffic situations

is safe and will stay safe. The controller will need to have knowledge on the location, intent, and

current clearances for each individual aircraft.

3.4.8 Handle different meteorological conditions

Requirements on meteorological conditions specify the specific situations that will need to be handled on the

Endless Runway under any possible weather situation.

REQ-ATM-14 The Endless Runway shall allow operations under low wind conditions.

In low wind conditions, cross- and tailwind will be less important and a wide range of take-off and

touchdown points can be used to enhance the capacity.

REQ-ATM-15 The Endless Runway shall allow operations under high wind conditions.

Taking-off and landing without crosswind and tailwind will be possible, as the traffic streams from

and to the runway will be “moving” with the wind.

REQ-ATM-16 The Endless Runway shall allow operations under all visibility conditions.

Main questions are whether aircraft must be able to see each other and whether the controller

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must have a visual view of the traffic as required today. Systems may be designed to assist pilots

and controllers.

REQ-ATM-17 The Endless Runway shall be operative under snow, rain, and icing conditions.

3.4.9 Environmental aspects

Requirements on environmental aspects include the possibility to optimize airspace operations to reduce the

impact of air traffic to the society in terms of emissions, noise, and third party risk.

REQ-ATM-18 Departure and arrival routes should be designed such that they will allow avoiding

overflying given areas.

It can be assumed that the airport is located near a large residential area, so that at least part of

the area around the airport will be defined with reduced nuisance.

Analysis 4.

This chapter gives an analysis of various aspects of the Endless Runway, based on the requirements set in

chapter 3. This chapter, therefore, is organised in the same way as chapter 3.

The analysis in this chapter will be based on:

Earlier work and patents concerning circular runways as described in the Endless Runway

state-of-the-art document [3]. As much as possible, experiences and ideas from previous research will

be considered when analysing the requirements.

The state-of-the-art description on various runway aspects from the same document will ensure that

the latest state of technology is considered in the analysis. Just as well, future visions for the air

transport system will be considered as the concept is meant to be for around 2050.

The results from the brainstorm session held with experts will help to bring in new ideas and to

consider as much as possible aspects when analysing the requirements.

Based on this review, a number of assumptions can be made; for example, it can be assumed that ILS will be

replaced by a system, such as satellite navigation, that will enable curved approaches.

The analysis will further elaborate on the requirement topic and propose one or more high level solutions

within the context of the requirement. Possibly, more than one requirement is dealt with in the analysis.

All analyses together constitute the operational concept for the Endless Runway.

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4.1 Methodology

Each separate analysis will be set up as follows.

Requirement number Brief description (one line)

Requirement text (more than one requirement can be named here)

Background literature

Assumptions and other remarks

Analysis

4.2 Airport design

4.2.1 Size of the circle

REQ-DESIGN-01 Define the size of the circle based on aircraft movements.

The runway circle shall allow a sufficient number of operations for the following types of airports:

Seasonal non-hub airports, including a mix of aircraft where mid-size aircraft are predominant.

Large, non-seasonal hub airport with a strong home carrier that operates mostly large aircraft.

large airports with a mix of aircraft, including mid-size and large aircraft.

Background literature from:

D1.2 State of the Art, chapter 3

Assumptions:

The following assumptions are made:

The arrival/departure rate is 50% arrivals and 50% departures.

The transfer rate is in the range of 50%-60%.

Hub airports usually have surges of arrivals and departures. Despite that there will always be

departures during arrival peaks and vice versa, the mixture of both will be relatively low.

Arrivals usually determine the airport capacity because the possible number of movements per

hour in departures is higher than the number of the former.

Analysis:

The size of the circle will depend on the estimated airport users’ demand. The number of movements in a

set amount of time (the airport capacity) must satisfy the needs of the demand. Several mathematical

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models yield accurate approximations as far as capacity estimation is concerned. A mathematical model

from Blumstein mentions that capacity depends on the:

• length of the final approach path,

• speed on final approach,

• runway occupancy time,

• traffic mix.

Another frequently used method is given in [4].

Taking into account that the final approach in the Endless Runway will be curved, separation between a

leading aircraft and the following one will probably differ from current ones with straight runways.

Analogously, speeds on final approach might be different, as the aircraft will be making a turn. These special

features will also affect runway capacity.

Further analysis on previous explained methods for estimating airport capacity will be carried out in WP2 of

this project. In order to provide a rough order of magnitude of the size of the circle, considering REQ-ATM-

01, which states that simultaneous movements on the Endless Runway must be possible, a hub airport with

radius R=1500m, would be equivalent to three straight runways. This is the number of runways functioning

simultaneously in a typical hub airport. This conservative approach could allow at least the same number of

operations than a hub airport with three runways. The Endless Runway concept should even improve this

number of operations for an equivalent straight runways’ set and reduce the airports’ airfield area.

REQ-DESIGN-02 Define the size of the circle based on airport facilities

The runway circle shall offer sufficient space for the most important airport facilities to be constructed inside

the circle.


D1.2 State of the Art: chapter 3

Assumptions:

The following assumptions are made in order to estimate the required size of the airport landside

infrastructure:

10,000 passengers per peak hour

Required space per passenger: 20 m2pph (per passenger hour)

On the airside, the following table presents data for calculating the number of stands necessary to serve the

aircraft:

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The standard international stand length is 65 m, the standard national stand length being 45 m.

INT NAT

Time in stand 105 min 50 min

Separation time 15 min 10 min

Total peak 60 60

International peak 75 45

National peak 50 68

Analysis:

The required landside size will be established by analysing several parameters. Based on the geometry of the

terminal building and its stands, the necessary number of stands, and the required space for passenger

comfort in the proposed infrastructure will be calculated.

Geometry

The first step consists of selecting the optimum geometry taking into account mainly the following points:

Airport landside geometry design taking into account specific location characteristics, as

geographical and demographic aspects

Easy orientation of passengers inside the terminal building and between terminal buildings in

case of more than one terminal is required

Crossing of passenger flows avoided

Short distances inside the terminal

Short distances for baggage transport systems to the aircraft

Minimum distances from parking lots to the terminal buildings and from terminal buildings to

aircraft

Compatibility with existing aircraft and sufficient flexibility in order to adapt to future

generations of aircraft

No incompatibilities between aircraft and terminal buildings

Easy aircraft manoeuvring

High percentage of airport fingers

For the Endless Runway concept, all these requirements could be accomplished by a circular shaped

terminal, or something with equivalent geometry.

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The size of the terminal building will be calculated in order to estimate the minimum size of the runway

circle that will allow enclosing the necessary terminal buildings. Two approaches are followed: one based on

the number of required stands and one based on the area required for estimated passenger flows.

Minimum size of airport facilities: Terminal

In Appendix A, a calculation for the number of stand and the required total airside length is provided. The

number of national and international stands taking into account flexible stands is 172. The total associated

airside perimeter is 10 280 meters.

Minimum size of airport facilities: estimated passenger flow

Taking into account 10 000 passengers per peak hour and 20 m2/pph, the necessary terminal area size will

be 200 000 m2. This area could be accommodated inside the 1500 meters radius circle (REQ-DESIGN-01).

Based on the total area required for the passengers (200.000m2), and simplifying the circular geometry to an

hexagon structure with the same area, airside length could be deduced:A = 31.5

·t2/2 (with A: area of hexagon

and t: side of hexagon); A = 2.105 t = 277 m

Total airside perimeter (for an hexagonal terminal): m

Combination of both calculations shows that the estimated number of aircraft cannot be parked around one

terminal. Therefore, different configurations could be set in order to fulfil the requirements:

1. Airport Terminal configuration in several floors. Based on calculated figures, more than 6 floors

should be required, to accommodate all aircraft stands required. This configuration could be

established by a terminal with underground floors in order not to construct a too high building.

Despite of that, 6 floors seem to be too demanding.

A preliminary idea concerning this concept could be that aircraft could park on an underground

platform (like aircraft carriers), where a special moving platform will provide access to the ground

contact stands. In this case, the aeroplanes would access this elevated stand by a special

mechanism.

2. Several satellites or midfield concourses around the main terminal. If this high-level requirement

on the number of stands is maintained, and still considering 3 floors, the total airside perimeter

available around the 3-floors terminal would be:

Thus, the airside perimeter available for the satellites is 5294 m. If three satellites were adopted,

the airside length for each one would be:

, which would lead to a terminal whose

size allows the building to be placed inside the runway. In order to calculate the walking distances

for originating/terminating and transfer passengers and considering the assumptions made above,

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two configurations are analysed: linear and x-shaped.

o linear satellites:

Ldl = 1765/2 ≈ 882 m

DO/T = Ldl /4 + 450/3 = 882/4 + 150 Ldl ≈ 371 m (walking distance of originating

and arriving passengers)

DT = Ldl /3 = 882/3 ≈ 294 m (walking distance of transfer passengers)

o X-shaped satellites:

Lx = (1,765+4·100)/8 ≈ 271 m

DO/T = Lx /2 + 450/3 = 271/2 + 150 ≈ 286 mDT = 0.25·(Lx /3) + 0.75·( Lx/2 + Lx/2) ≈

226 m

X-shaped terminal will be preferred over linear because distances are smaller, although they cannot

accommodate aircraft at the centre.

REQ-DESIGN-03 Location of non-aircraft handling related airport facilities

The runway circle should offer sufficient space for other airport facilities to be constructed inside the circle.



Assumptions:

The size of the circle is estimated based on airport capacity and aircraft performance. Airport facilities are

X-shaped terminals configuration

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preferably positioned inside the runway circle.

Analysis:

Apart from the calculation of the required space for terminal building settled in the previous section, it is

desirable to accommodate other facilities inside the circle so that the airport becomes more compact than

conventional airports. Facilities taken into account are: cargo areas, mail facilities, fire stations, and

maintenance hangars.

It should be pointed out that all these facilities must not be visual obstacles for the Control Tower that is

envisaged to be in the centre of the main terminal (centre of the circle), as stated in REQ-DESIGN-11.

Emergency services

The need for emergency services is defined by ICAO, who recommends a certain level of protection against

fire. The mission of emergency services consists of:

Aid to passengers and crew after an accident has occurred.

Mitigation of possible aircraft damages in the case of an accident.

Prevention and reduction of fires in airport facilities.

The time between the phone call to the fire station and the application of the foam by the first vehicle is

stipulated by ICAO Annex 14 to be 2 minutes and never more than 3 minutes. In case several stations are

needed, they would be distributed among the area by circular sectors in a way that they can reach each part

of the airport in 2 minutes. This location must allow immediate, direct and safe access to any part of the

airfield without crossing the runway, taxiways or difficult terrain, and not interfering with the control tower

line of sight.

Hangars

With respect to hangars, their aim is to preserve aircraft from being damaged by atmospheric conditions. In

general, airlines have their own hangars, where inspections and maintenance tasks are performed. The size

of hangars for commercial aircraft is usually around 100 m. A generic decision concerning the location of

hangars cannot be made without further knowledge of the available space inside the runway circle. Hangars

should preferably be located inside the circle, but further study needs to determine if it is possible to

allocate them inside the available space.

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4.2.2 Bank angle

REQ-DESIGN-04

REQ-DESIGN-05

REQ-DESIGN-06

Bank angle

Wingtip, engine, and tip-back angle clearance

Bank angle at the hump of the runway

The runway, with a given radius, shall have a gradually increasing bank angle allowing take-off and landing

speeds for the aircraft intending to operate on the runway.

The bank angle of the runway shall consider engine clearance, wingtip clearance, and the tip-back angle

(during take-off rotation) of the aircraft

The link between taxiways and the runway shall not contain abrupt transitions.



Assumptions and other remarks

-

Analysis:

The runway will have a range of bank angles that will match the aircraft’s flight profile and passenger’s

comfort. A maximum bank angle of 25º, can be assumed to be acceptable for passengers. The inner part of

the runway will be flat, while the bank angle will reach its maximum at the outer part of the runway. Wing

tip clearance must be assured. A safety area must be provided inside and outside the runway.The transverse

slope of the Endless Runway will change significantly compared with a straight runway. Particular points of

interest are runway entry and exit points. An absence of discontinuities is required.An analysis of the

different existing aircraft geometries will lead to know the adequate slopes that surrounding ground must

have. Drainage of the runway (evacuation of water, de-icing fluids…) should be considered as well.

Taxiways should have an excess width at their entrances in order to provide high-speed exits of the runway.

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4.2.3 The layout of taxiways and aprons

REQ-DESIGN-07

REQ-DESIGN-08

REQ-DESIGN-09

High-speed exits/entries and runway holding areas

High-speed exits should be available to minimise the runway occupancy times of arriving aircraft.

High-speed entries should be available to minimise the runway occupancy times of departing aircraft.

A runway holding area shall be designed.



Assumptions and other remarks:

-

Analysis:

Taxiways serve as the runway entry point and play an important role. They will mostly be located at the

inner area of the circle.Most airports use high-speed exits to increase capacity. As the landing aircraft

describe a curved trajectory, it is natural that the aircraft exits would be curved too, with an inferior radius.

ICAO and FAA rules prescribe that a high-speed exit forms an angle significantly lower than 90º with the

runway centreline.

High-speed exit taxiway (source: McGraw-Hill Dictionary of Aviation)

The ICAO also stipulates that the turn-off curve of a high-speed exit should be at least 550 m to allow exit

speeds of 93 km/h under wet surface conditions for ICAO code numbers 3 or 4 aircraft. Mid-sized and large

aircraft can leave the runway in safety conditions with speeds ranging from 95 to 105 km/h. A commonly

used angle between the runway and the high-speed exit centrelines is 30º, which enables an aircraft to turn

while travelling at 90 km/h. Mid-sized aircraft are capable of using angles at 45º and 65 km/h.

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If aircraft performance does not change significantly, then these numbers should be applied to design

taxiways. The smaller the radius of the Endless Runway will be, the steeper the high-speed exit angle will

become. Therefore a bigger circle would allow aircraft to leave the runway at higher speeds, optimizing the

use of the latter.

The radius R of an exit is calculated by means of the following formula, with V the aircraft speed and a the

aircraft acceleration set to 1.304 m/s2:

The following table shows usual figures for the layout of

Code Angle at Central Exterior Width of

1 or 2 45º 275 m 253 m 21/18/12

3 or 4 30º 550 m 488 m 27 m

All 90º 75 m 53 m 27/20

Circular Runway: runway exits, entrances and taxiways

The figure above presents a scheme of high speed exits

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Holding bays can be constructed adjacent to entry/exit points in

order to prevent collisions and offer a waiting area for aircraft

waiting to take-off. A solution for this would be to design an

entry/exit taxiway with a small radius inner circle and an exterior

substantially bigger circle, inside the runway circle. As shown in the

figures, the holding bays are contained in a surface that includes

the high-speed exits. This would allow a wide area where aircraft

could wait for ATC clearances.

REQ-DESIGN-10 Taxi routes

Taxiways shall be designed in a way to minimize the




-

Analysis:

Taxiway planning must be integrated in the overall airport

In order to minimize costs and operation time, straight

4.2.4 The location of the control tower

REQ-DESIGN-11 Control tower location

The control tower should be located at the centre of the



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Assumptions:

Analysis:

The location of the control tower location is one of the

It must have a sufficient height so that good visibility over taxiways and runways is ensured.

It must be built in a smoke and noise free area.

It must provide capacity for personnel to accommodate the number of aircraft, type of aircraft,

number of movements and relative positions between them in the airfield.

The line of sight must be perpendicular or inclined in relation to the aircraft trajectory and intercept

the surface that has to be controlled with a slope higher than 1% (1.5% is the ideal slope).

With regard to the orientation to the sun, approaches in the direction of dawn and sunset must be

prevented.

Access routes to the control tower should avoid crossing areas where aircraft operate.

Its location shall not be inside obstacle free zones.

At sight level (1.3 m), air traffic controllers have to distinguish aircraft and vehicles that operate in

the airfield.

For the Endless Runway, a control tower located at the

An alternative is to operate a virtual tower, where

4.2.5 Terminal buildings, hangars, maintenance area, fire building, etc.

REQ-DESIGN-12 Construction and interior of terminal

Terminal buildings shall be constructed such that they will




-

Analysis:

The main types of airports passengers are: domestic or

Transfer passengers have special needs. They value fast,

The terminal design will be further worked out in later

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REQ-DESIGN-13

REQ-DESIGN-14

Gates and stands

Gates and stands shall be located at the airport in such a




-

Analysis:

Aprons provide the interface between landside and

Safety must be preserved while allowing the maximum number of aircraft movements. According to

ICAO, the following minimum clearances have to be provided at an aircraft stand between any part

of the aircraft and any adjacent building, aircraft on another stand, or other object, except for

vehicles and equipment servicing the aircraft:3 m for code letters A and B

4.5 m for code letter C

7.5 m for code letters D, E, and E.

The dimensions of the stands are important. Excessive

Concerning the number of stands, at seasonal non-hub

With regard to hub airports, a midfield linear concourse

At large airports, as gates will be used continuously

REQ-DESIGN- Stakeholders needs

Airport stakeholders’ needs shall be taken into account.




-

Analysis:

Airlines, specifically home carriers or a major hub

Airport owners like architectural masterpieces but on the

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Government agencies can often constrain the development

To conclude, several stakeholders have their role in

REQ-DESIGN-16 Hybrid terminal configurations

Hybrid configurations (consisting of a mixture of




-

Analysis:

Nowadays no consensus exists whether centralized or

To conclude, centralized buildings offer more

4.2.6 Access to the airport

REQ-DESIGN-17 Curb-side location

Curb-side roadways should be located so that no




-

Analysis:

The runway configuration may restrict ground access to

Another option would be to construct the curb-side

REQ-DESIGN-18 APM vehicles

Automated People Mover vehicles should be used in order



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-

Analysis:

In order to access the facilities located inside the circle of the Endless Runway, APM (Automated People

Mover) systems may be needed. Indeed, if there is not sufficient space inside the circle to expand the

existing terminal, an external terminal (satellite) may be a solution.An extensive description of APMs can be

found in Appendix B.

Studies should be carried out in order to decide whether

Three types of airports are considered in this report:

Seasonal non-hub airports, including a mix of aircraft where mid-size aircraft are predominant.

Large, non-seasonal hub airports with a strong home carrier that operates mostly large aircraft.

Large airports with a mix of aircraft, including mid-size and large aircraft.

For the first type, transporters would provide the most

For the other airport types, APMs seem favourable

REQ-DESIGN-19 Access routes

In order to satisfy users’ needs (originating and




-

Analysis:

Nowadays, automobiles and buses are the preferred

In order to plan the ground access system, a study

4.3 Aircraft aspects

4.3.1 Passenger comfort

REQ-AIRCRAFT-01 Passenger comfort

The endured acceleration during the curved ground roll at take-off and landing shall not exceed sustainable

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values for passengers’ safety and comfort.


D1.2 state-of-the-art description: §2.3.2.2.1 and §2.3.2.2.2

Brainstorm ideas


It assumed that the load factors applied to the aircraft are within the structural limits as mentioned in the

flight manual.

Analysis:

As for all transportation means, vehicles are manoeuvred in order not to exceed given longitudinal and

centripetal accelerations acceptable by passengers. In flight, just after take-off or prior to landing, the

aircraft is rolled to match the runway bank angle. This nominal condition for today’s aircraft generates load

factors sustainable by passengers, equal to:

Bank angle Load factor

0° 1 g

15° 1,03 g

25° 1,1 g

During a ground roll on the circular runway, passengers support both the longitudinal and the centripetal

acceleration, according to the following formulas:

A comparison with trains, shows that they are designed so that passengers do not sustain a lateral

acceleration higher than 1,2 m/s2, which corresponds to 0,23 g. This value can be used as an initial reference

for our aircraft study.

The total acceleration is:

√

An appropriate aircraft acceleration and deceleration during the ground roll could help optimizing passenger

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comfort. Indeed, in order to thwart the effect of the centrifugal force, a strong longitudinal acceleration

during the turn might give a positive feeling to passengers, since it would displace the acceleration vector in

the direction of the turn. A similar reasoning applies for landing.

On the following figures, the aircraft trajectory is represented by a curved dotted line. The speed vectors at

t1 and t2 (with t1 < t2) are named and

. The direction of the acceleration is the one of the vector

, due to the acceleration formula (

). It is not the purpose of the scheme to show the norm

of the acceleration vector. What is shown here is that the stronger the longitudinal acceleration, the more

the effect of the lateral acceleration is limited when considering the total acceleration.

A stronger acceleration than on a standard straight runway would imply a change in engines dimensioning,

which will also reduce the take-off length.

A stronger deceleration than on a standard straight runway would imply stronger landing gears and resistant

tyres as well as a reduced landing length.

𝑉

𝑉

𝑉

𝑎

Take-off: progressive acceleration

𝑉

𝑉

𝑉 𝑎

Take-off: strong acceleration

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4.3.2 Take-off and landing parameters

REQ-AIRCRAFT-02 Take-off and landing speed

The take-off and landing speeds shall be within the maximum speed allowed by the runway.




-

Analysis:

Each imaginary circle of the circular runway corresponds to an optimum aircraft speed with the

relationship . The take-off speed has to be reached before the hump of the runway

(corresponding to the maximum allowed speed).

REQ-AIRCRAFT-03

REQ-AIRCRAFT-04

Landing point

Take-off point

The aircraft shall land at a precise point at a given speed and a given bank angle.

The aircraft shall take-off at a precise point at a given speed and a given bank angle.

𝑉

𝑉

𝑉

𝑎

Landing: progressive deceleration

𝑉

𝑉

𝑉

𝑎

Landing: strong deceleration

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D1.2 previous research and patents

D1.2 state-of-the-art description

Brainstorm ideas

Discussion during a teleconference between the Endless Runway partners


Taking-off and landing with headwind is considered as optimum. Aircraft land and take-off with a smaller

ground speed and with a smaller take-off distance in headwind conditions. Moreover, landing and taking-off

with headwind requires less bank angle and with tailwind a larger bank angle, because of the relation

between the aircraft ground speed and the runway bank angle.

The aircraft bank angle at landing and take-off does not exceed current values found in the flight manuals.

Bank angle description Value (°)

Nominal bank angles for civil flight during TO and LD 15

Maximum bank angles for civil flight during TO and LD 25

Analysis:

Landing and take-off segment / landing and take-off point:

The take-off and landing segments are provided by the ATC as a function of the other traffic and wind

conditions. In low wind condition, the best point will be computed based on optimisation of aircraft

trajectories and airport capacity considering other traffic. Above a certain wind speed, the location of the

aircraft ground roll during take-off and landing is optimized according to wind direction and speed.

Due to the circular shape of the runway and to the fact that there cannot be headwind all along the ground

roll, it should be further analysed if, in terms of landing distance, it is optimal to face the wind at the

touchdown point or after. The same question can be raised for the lift off point.

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Aircraft landing run versus wind direction

or

?

?

Lift-off point

?

?

or

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Take-off and landing speed

The computed landing speed1 of the aircraft will correspond to a bank angle that the aircraft will have to

adopt in order to land on the right position of the circle. The computed take-off speed of the aircraft will also

correspond to a certain bank angle and thus to an imaginary circle from where the aircraft will take-off.

Bank angle

Aircraft configuration shall allow the aircraft control at low speed at the bank angle of the runway in

asymmetrical flight conditions. To maintain low speed asymmetrical flight, control surfaces are already

deflected, much more than at high speed. In case of an emergency manoeuver (obstacle or collision

avoidance), the required control surface deflection may exceed the available range. Therefore, for an aircraft

tailored to the Endless Runway concept, the control surface layout should define additional safety margins.

REQ-AIRCRAFT-05 Take-off and landing slopes

Take-off and landing vertical slopes shall be high enough to avoid any contact between the extended landing

gears and the higher part of the runway when the aircraft is airborne and overflying the runway.


-

Assumptions and other remarks: This requirement applies to aircraft with slow take-off and landing speeds.

Analysis:

Aircraft taking-off at low speed will become airborne on the inner part of the runway. Since there is a strong

ATC constraint that they clear the runway as soon as possible, they will fly towards the external part of the

runway rapidly after rotation, in extended landing gears conditions. Due to the curvature of the runway, the

pilot must ensure a sufficient clearance between the landing gears and the hump of the runway. This can be

achieved through a sufficient take-off slope.

The same reasoning applies to aircraft landing at low speed.

1 Refer to flight manual for parameters (such as aircraft weight, pressure altitude) to be accounted for in the landing speed

Vref and take-off rotation speed Vr computation.

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4.3.3 Landing gear

REQ-AIRCRAFT-06 Landing gear strength

The landing gear shall be able to withstand the loads generated during landing.




-

Analysis:

Landing loads are higher than take-off loads. They are thus the limiting loads for the landing gear. On a

circular runway, it may happen that the load is stronger on the external landing gear, if the aircraft is not

banked enough at landing for example. This overload on one landing gear should remain in the acceptable

limits from the regulation (e.g., EASA CS-25) or landing gears should be reinforced.

REQ-AIRCRAFT-07 Landing gear layout

The landing gear layout shall provide satisfactory stability during ground run (take-off and landing).


-


-

Analysis:

Larger wheel base and track would offer more stability on a banked runway. Furthermore, a bigger distance

between the main landing gears would provide a safer engines and wingtips clearance.

Illustration of landing gear characteristics (wheelbase and track)

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The solution selected by Bombardier on the Q400 (main landing gears under the engines) could be

considered:

Q400 landing gear layout

4.3.4 Engines

REQ-AIRCRAFT-08 Engines selection

Engines forces should consider a ground run on a circular and therefore non-symmetrical runway.


The Endless Runway kick-off meeting


-

Analysis:

Because of the asymmetrical ground run of the aircraft, the thrust applied on each engine might be different

than that for operating a conventional runway:

1. One-directional operations. The optimized aircraft configuration may have different engines size on

each side of the aircraft.

2. Two-directional operations. Because of the required flexibility, engines sizes would be the same but

throttle position might differ.

For both options, One Engine Inoperative (OEI) conditions shall be considered: the aircraft shall be able to

maintain the desired trajectory with only one engine operative. Two asymmetrical cases need to be verified:

the loss of one external engine would steer the nose towards the outside of the runway, whereas the loss of

one internal engine would steer the nose towards the inside of the runway.

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4.3.5 Aircraft ground clearances

REQ-AIRCRAFT-09

REQ-AIRCRAFT-10

Aircraft clearance with ground

The tip-back angle of aircraft should be tailored to the runway transversal profile to avoid ground contact

during take-off rotation.

The aircraft configuration shall ensure clearance between aircraft components (e.g., wingtips and engines)

and the banked runway.

Background literature:



-

Analysis:

Tip-back angle

The tip-back angle is defined by the tangent line between the rear landing gear and the fuselage. On this

picture, the same tip-back angle is achieved with different height of landing gears.

The following figure shows the aircraft tip-back angle and its reduction, because of the bank angle of the

runway. Due to the continuous change of the bank angle and associated change of curvature, at the rotation,

the tip-back angle is smaller than on a conventional runway. Just as well, when entering or leaving the

banked runway track, the aircraft will be positioned slightly transversely to the runway direction, which may

lead to loss of ground clearance.

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Although the longitudinal stretch of the banked runway will be flat with respect to the aircraft, it must be

assumed that during take-off and landing, the aircraft may position itself a bit off its optimal take-off and

landing point. At those moments, clearance of the tip-back angle of the aircraft must be ensured.

Wingtip

The wingtip height will be reduced on a curved runway track as indicated in the following figure.

A high wing construction will be a preferable option to ensure maintaining a certain clearance. In this

manner, limitations due to high aspect ratio wings2 could be reduced. The following figure shows a future

aircraft with a high aspect ratio of the wings on top of the fuselage.

2High-aspect ratio wings are long and slender wings.

Standard tipback angle

Reduced clearance

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Typical wingtip heights on a flat runway are indicated in the following table. Clearance from the bank angle of

the runway will depend on the design of the bank angle.

Aircraft type Aircraft description ICAO code Wingtip height (m)

Large Boeing B737-300/

CFM56-3B-1 Engines

B733 3

Mid-sized Airbus A320-232/

V2527-A5 Engine

A322 3.7

Regional Saab SF340B/

CT7-9B Engines

SF34 2.5

Business jet Dassault FALCON 20/

CF700-2D-2

FA20 1.5

Military bomber Rockwell B-1 Lancer B1 3.6

General aviation Diamond DA 40 DA40 0.73

Engine

Engine clearance is similar to wingtip clearance. Since the shape of the bank angle is not yet decided, no

further information can be provided here yet.

A bigger distance between the main landing gears would provide a safer clearance.

4.3.6 Situational awareness for the pilot

REQ-AIRCRAFT-11

REQ-AIRCRAFT-12

Pilot’s situational awareness

The flight crew shall receive the landing or take-off point in negotiation with ATC.

The flight crew shall be able to follow the take-off and landing sequence thanks to appropriate on-board

navigation systems.



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-

Analysis:

In context of the vision for 2050, it is assumed that the pilot will have all required information presented on

cockpit displays for situational awareness, not only from the aircraft point of view (attitude, location, etc.),

but also from the ATM perspective (surrounding traffic and planned trajectories displayed for traffic collision

avoidance). Current vision documents indicate the pilot will have more a management function to oversee

the aircraft’s behaviour, where at any time, he will have the possibility to override the automated take-off

and landing sequence.

Current developments in cockpit design and human factors, like augmented reality, indicate that display

technology will be available to enable the pilot to receive all information required to manage the aircraft.

4.4 ATM procedures

4.4.1 Runway Operations

REQ-ATM-01 Runway Operations (simultaneous use)

Simultaneous use of the runway shall be allowed.


D1.2 state-of-the-art description: §6.7.1


Today’s operation follows the rule that the runway can be used by one aircraft only at the same time for

take-off or landing. Multiple threshold operations are implemented to reduce separation minima but not to

use the runway by more than one aircraft.

Depending on the radius of the circle, the Endless Runway should be large enough to operate more than one

aircraft at the same time taking into account common required distances for take-off and landing (including

safety distances in case of an aborted take-off or runway overshoot). To achieve the required capacity of the

airport, simultaneous use of different parts of the runway should be allowed.

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Analysis:

The table below shows:

Available distances with different radius values (circumference )

Number of runways in comparison with typical straight runway length (nr=circumference / runway

length)

Radius (m) Circumference (m) Number of Runways

Straight runway length of conventional airports

2,500m 3,000m 4,000m

500 3,141.59 1,26 1,05 0,79

1000 6,283.19 2,51 2,09 1,57

1500 9,424.78 3,77 3,14 2,36

2000 12,566.37 5,03 4,19 3,14

For example, with a 1500m radius there would be room for approximately three separate runway sections of

around 3000 meters.

If the runway is subdivided into more than the number of full runways from the table above, a dedicated

operational concept can lead to an optimized use of the circle. The figure below shows the runway separated

into 36 segments, where one circumventing taxiway provides access to every segment at the runway and

taxiways connect the circumventing taxiway every three segments.

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28

29

3130

3534

33

32

369

87

6

5

4

32

11

011

12

13

14

15

1617 18 19

2021

22

23

24

25

26

27

Terminal

Runway segments

Taxiways

Apron

The concept for the use of the circular runway as a number of segments is as follows:

A number of segments linked together form a temporary runway strip.

Each flight can claim a number of segments for a certain time for departure or arrival. The number of

segments is related to the required take-off or landing distance.

A safety distance between claimed segments is added by ATC.

Each segment is reserved to one flight at a specific time. It can be freed after a short safety period

for the next movement. This concept has to be defined in terms of safety and operational feasibility.

The segments claimed by different aircraft can be optimized for taxi operations, wind, and departure

direction of each individual flight.

Each aircraft is capable of calculating the required runway length for its operation based on the actual aircraft

status (weight), the runway conditions and actual weather information. A runway strip with the respective

length has to be reserved for the movement. In addition safety buffers should to be added to cover small

deviations and inaccuracies.

Two safety zones must be included: one in front of the final point of the required runway strip for accidental

overruns and one behind the actual position of the aircraft to avoid jet blast. The part of the runway strip

that was reserved and is not needed anymore (aircraft already passed) and can be claimed by the next

aircraft.

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28

29

3130

3534

33

32

36

98

7

65

4

32

1

10

11

12

13

14

15

1617 18 19

2021

22

23

24

25

26

27

Terminal

AC2

Apron

AC1

Safety buffer front

moving Safety buffer back

These segments can be freed

already

Actual aircraft position

REQ-ATM-02 Runway Operations (Direction of operation)

The direction of operation should be flexible.




The runway can be operated clockwise or counter-clockwise uniquely or even in opposite mode. This allows

the most flexible use of the resources as long as safety can be assured.

Analysis:

High wind scenario

Only two areas for take-off or landing are available to avoid heavy crosswinds. To use both areas opposite

traffic is allowed as long as the required distances (take-off or landing) are available and a safety buffer is

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assured, as depicted in the figure below.

Safety Zone

Touchdown AC1

Touchdown AC2

Touchdown Area 1

Wind Wind

Touchdown Area 2

Low wind scenario

In low wind conditions the runway can be used in a very flexible manner. Both directions (clockwise and

counter-clockwise) can be operated separately or simultaneously, as shown in the figure below.

Touchdown AC1

Touchdown AC2

Touchdown AC3

Touchdown AC1

Touchdown AC2

Touchdown AC3

Clockwise operations Counter-clockwise operations

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While in high wind conditions the operations will be probably in opposite directions, in low wind situations

this might be related to the traffic load. In peak hours all aircraft should be operating in the same direction

(clockwise or counter-clockwise) to use the runway resource to the limit. Outside peak hours, optimisation

could lead to use of the runway in opposite operations as well.

Safety zones

When operating in opposite directions, a safety zone shall be defined to avoid critical situations. The safety

shall not be penetrated by the planned runway strip. The size of the safety zone can be adapted dynamically

and is related to the meteorological conditions and the current aircraft characteristics.

REQ-ATM-03

REQ-ATM-04

4D operations and controller decision support tools

4D-operations shall be available.

Coordination support tools shall be available.


D1.2 state-of-the-art description: §6.2.2.1


A 4D-operational concept (like in SESAR) is implemented at the airport and aircraft arriving and departing are

equipped accordingly.

The high complexity of the operation cannot be handled without system support. The controller will not be

able to coordinate the movements and actively control each aircraft by monitoring and giving instructions.

Therefore appropriate systems are in place to support the human.

Data link communication is improved and airport and aircraft are equipped with fast high bandwidth systems.

Therefore a high level on information sharing is available.

Analysis:

In accordance with the basic concept of the segmented runway operation, time based coordination must be

made available. The 4D-trajectory is extended and available from gate to gate (on block/off block).

Runway segments can be claimed by every aircraft arriving or departing at the airport. Based on the favoured

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arrival/departure path and the taxi distances on the ground, the optimal segments can be calculated for each

flight. The Flight Management System (FMS) of the aircraft will then calculate the timeframe for take-off or

landing. Based on these parameters a booking procedure must be initiated checking the availability of the

runway segments at this time:

If the runway is available, a contract between the airport and the aircraft will be put in place.

If the runway is not available, more negotiation will take place between aircraft and airport until a

feasible operation is found. Based on the new parameters the contract will be placed and the FMS of

the aircraft will calculate a new 4D trajectory to meet the required times.

In combination with multiple runway operations and 4D operations, a support tool must be available that

allows negotiations between aircraft and airport. A planning system will coordinate the requests from aircraft

and optimize the available runway resources. Depending on the combination of arrivals and departures

(aircraft types) in a given time frame, optimisation will be necessary to ensure safe operation to allow a

maximum use of the capacity.

The figure below shows an example of how runway segments can be allocated to particular flights in a time

based manner. Segments can be booked by two flights in a short timeframe. This could be possible when the

leading aircraft has already left the first segments even when it still uses the last ones (for example: KL33777

can use segments 15-18 while AF6666 still occupies segments 23-26).

Time from Time to 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36

08:00 08:01

08:01 08:02

08:02 08:03

08:03 08:04

08:04 08:05

… …

Segment

LH 1234 AF6666

IB 1111 KL 3377 IB 1111

With an increasing number of segments of the circle, the required runway strip for an aircraft can be

allocated with more precision. The number of unused resources is reduced to a minimum and capacity is

maximized. In return for the raising number of segments, the required computing capacity will increase

significantly.

Analysis:

In accordance with the basic concept of the segmented runway operation, time based coordination must be

made available. The 4D-trajectory is extended and available from gate to gate (on block/off block).

Runway segments can be claimed by every aircraft arriving or departing at the airport. Based on the favoured

arrival/departure path and the taxi distances on the ground, the optimal segments can be calculated for each

flight. The Flight Management System (FMS) of the aircraft will then calculate the timeframe for take-off or

landing. Based on these parameters a booking procedure must be initiated checking the availability of the

runway segments at this time:

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If the runway is available, a contract between the airport and the aircraft will be put in place.

If the runway is not available, more negotiation will take place between aircraft and airport until a

feasible operation is found. Based on the new parameters the contract will be placed and the FMS of

the aircraft will calculate a new 4D trajectory to meet the required times.

In combination with multiple runway operations and 4D operations, a support tool must be available that

allows negotiations between aircraft and airport. A planning system will coordinate the requests from aircraft

and optimize the available runway resources. Depending on the combination of arrivals and departures

(aircraft types) in a given time frame, optimisation will be necessary to ensure safe operation to allow a

maximum use of the capacity.

The figure below shows an example of how runway segments can be allocated to particular flights in a time

based manner. Segments can be booked by two flights in a short timeframe. This could be possible when the

leading aircraft has already left the first segments even when it still uses the last ones (for example: KL33777

can use segments 15-18 while AF6666 still occupies segments 23-26).

Time from Time to 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36

08:00 08:01

08:01 08:02

08:02 08:03

08:03 08:04

08:04 08:05

… …

Segment

LH 1234 AF6666

IB 1111 KL 3377 IB 1111

With an increasing number of segments of the circle, the required runway strip for an aircraft can be

allocated with more precision. The number of unused resources is reduced to a minimum and capacity is

maximized. In return for the raising number of segments, the required computing capacity will increase

significantly.

4.4.2 Paths/Routing(Departure/Arrival)

REQ-ATM-05 Taxi routing

Airport taxi in/out routes shall be defined to allow the pilot to choose the most cost effective route from the

apron to the runway entry point and from runway exit to the gate.




-

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Analysis:

Full coordination of the departure and arrival routes from and to the gate should be implemented.

In addition to the airborne trajectory optimisation, the movement on the ground should be optimised too. In

that perspective, the following criteria have to be addressed:

Taxi-out Taxi-in

Meeting the claimed timeframe for runway use Distance from the runway exit to the parking

position

Distance from the gate to the departure point Number of stops and waiting times

Number of stops and queue waiting times Availability of the parking position

Necessary de-icing procedures

A ground movement management system can assist in calculating taxi times based on the traffic information

available. If the 4D-trajectory is fully available on the ground, decision support systems can coordinate all

expected movements and upload taxi information/recommendation to aircraft. Already existing brake to

vacate systems can be used to calculate the optimal runway exit and share this information with

management systems on the ground.

26

27

29

28

31

30

32

34

33

Start of the banked runway

taxiway for arrivals after leaving the runway + arrivals on the apron

Apron guidance lines

Highspeed exit lines from the runway (clockwise)

Runway center line

taxiway for departures going to the runway segment + departures on apron

Highspeed exit lines from the runway (anticlockwise)

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The number and position of exits and entries from/to the runway is relevant for the effective use of the

taxiway system. An efficient taxi route should be available independently from the direction of operation of

the runway (clockwise, counter-clockwise, or both directions simultaneously). In addition to the calculations

in 0, the following figure illustrates a possible approach where runway exits and entries are available at each

runway segment. This leads to an optimum use of the runway as runway occupancy times are reduced to a

minimum.

The figure contains the following elements:

High speed exits/entries may be used in both directions depending on the landing/take-off

direction.

One outer circular taxiway far enough from the Endless Runway track.

One inner circular taxiway.

Spoke connections between the inner taxiway and the outer taxiway.

Spoke connections between the inner taxiway and the airport inner area.

The airport inner area can consist of taxiways, aprons, buffers, and stands.

Greens (grass) between the Endless Runway and the outer taxiway, and between the outer taxiway

and the inner taxiway.

REQ-ATM-06 TMA routes

Departure/Arrival routes shall be defined that will allow the pilot to choose the most cost effective route

from the runway to the Terminal Manoeuvring Area (TMA) exit or from the TMA entry to the touchdown

point.


D1.2 state-of-the-art description: §6.2.2.1 and §6.2.2.2


In the TMA inbound and outbound traffic flows need to be handled. Next to that aircraft can make a missed

approach and need to be taken out of the inbound traffic flow and put back into the approach flow. Aircraft

can land and take-off from any desired location on the Endless Runway resulting in arrivals and departures

from any direction on the runway.

It is assumed that composite separations of 500 ft. vertically and 1.25 NM lateral can be applied as an

alternative to 1000 ft. vertical or 2.5 NM lateral separation. The 1 NM separation of the touchdown points

together with the time difference of around 40 seconds of subsequent landings results in safely separated

aircraft. The 40 seconds time separation is a result of the composite separation (500 ft. + 1.25 NM) applied

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between subsequent aircraft approaching inside the TMA.

4D-contracts are available.

Analysis:

Two different approaches to optimise the trajectories in the TMA will be described here: continuous turning

and free flight.

Continuous turning

The continuous turning approach path is positioned such that it lies on a cone shape. The cone shape fits the

Endless Runway shape, and allows for shallow bank angles at larger altitudes. Furthermore, it allows the

controller to level off an aircraft on the edge of the cone effectively having it fly a level turn. The controller

can let the aircraft continue the descent without giving vectors to line-up again. The following figure shows

the cone shape guiding the approach towards the Endless Runway.

The cone shape has a specified angle. It will allow applying a composite separation of 500 ft. vertically (half

of 1000 ft. normal vertical separation) and 1.25 NM laterally (half of 2.5 NM normal radar separation). The

cone shaped TMA has different circular layers separated by a composite separation of 500 ft. vertically and

1.25NM laterally, as depicted in the figure below.

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The controller can clear the traffic sequentially to a next inner circular layer. At each layer aircraft are

separated from the other traffic. Under normal operations the controller will re-clear the aircraft to the next

inner circle before the aircraft starts levelling off. In this way the aircraft can

normally land within the agreed touchdown area. The number of circular layers

applied is variable and can be adapted. The cone shape angle is set at 3.75 degrees,

as at this angle it is possible to apply a composite separation within the cone of 500

ft. vertically combined with 1.25 NM laterally.

Free Flight

The second approach is the implementation of a free-flight airspace where every aircraft can define the

route by itself. The basic idea (conform the free flight concept) is to define safety zones around each aircraft

that shall not be penetrated by safety zones of other aircraft, see the figure below.

As long as this separation can be achieved, every flight can define its flight path within the TMA. In contrast

to the continuous turning approach the routes would be more widespread through the TMA and probably

align with the banked runway at a very late stage of the approach. The responsibility of the separation

assurance has to be transferred to the aircraft.

While the size of the protected zone will be fixed, the size of the alert zone will vary with aircraft speed and

navigation capabilities. Possible size values of the zones have to be evaluated, as it has a direct impact on the

separation in the final flight phases and therefore on the achievable runway capacity.

4.4.3 Determination of take-off/touchdown points by ATC

REQ-ATM-07 Determination of lift-off/touchdown point

ATC shall be able to determine the optimal take-off and touchdown points for each individual aircraft, based

on the aircraft trajectory, cross- and tailwind limits and other traffic.

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4D operations are implemented.

Data link communication is available for traffic information sharing.

Analysis:

The determination of the lift-off/touchdown point is necessary to optimise traffic flows. ATC will monitor all

traffic flows and weather conditions to ensure safety and manage the allocation of the runway to the flights.

Different criteria are taken into account:

Aircraft trajectory

The FMS of aircraft will be able to calculate a full 4D trajectory from the TMA entry to the gate and vice

versa. This leads to a defined lift-off/touchdown point which is part of the overall trajectory. Continuous

descent and climb operations are preferred and should be implemented whenever possible and coordinated

between ATC and aircraft.

Cross and tailwinds

The operational use of the circular runway, defined by ATC, is dependent on the wind conditions. The

number and position of available take-off and touchdown points is closely related to the meteorological

conditions.

Low winds High number of points available (e.g., each segment can be used)

Medium winds Number of available points is related to aircraft type

High winds Low number of different points available (e.g., only two points can be used)

Traffic situation

ATC has to monitor the overall traffic situation and the trajectories of the aircraft in the vicinity of the

airport. In case of usage of several simultaneous lift-off/touchdown points, ATC shall be able to optimise

traffic flows in order to avoid congested areas with an increased risk of critical situations.

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4.4.4 Missed approach procedures

REQ-ATM-08 Missed approach procedures

A missed approach procedure strategically separated from the other traffic flows shall be available.


D1.2 state-of-the-art description: §5.1.3.2


It is assumed that the Endless Runway has enough free space around the airport for making radial climbs

outside the cone. If this is not the case the procedure can be restricted to use for instance a limited set of

outward radials (e.g., only 60, 180, and 300 degrees).

Analysis:

A missed approach can be initiated by the controller or the pilot. The missed approach can be initiated by

the pilot without providing the controller with prior knowledge, but he should inform the controller about

the missed approach as soon as possible.

According to FAA, the obstacle-free zone (OFZ) is aimed at providing clearance protection for aircraft landing

or taking off and for missed approaches.

The missed approach procedure is defined as follows. The pilot continues the flight in the cone shaped TMA

until reaching a height of a 1000 ft. Then the aircraft will make an outward turn and continue within the

cone to a height of 1000 ft. and then will take an outward radial and climb to a height of 4000 ft. The figures

below provide an idea of this procedure.

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4.4.5 Navigation aids

REQ-ATM-09

REQ-ATM-10

Navigational aids for take-off/landing

Ground based or space based navigation aids shall be available to assist the pilot to take-off and land with

high precision on any point defined on the circle in any visibility condition.

Ground based or space based navigation aids shall be available to assist the pilot to perform an Instrument

Departure or Instrument Arrival from and towards the Endless Runway.




To assist the pilots in the final phase of the approach, suitable visual guidance has to be available. Currently

runway markings and lighting are relevant. Actual definitions of these guidance elements are related to the

threshold of the runway.

In case of low visibility instrument flight rules have to be applied. Therefore suitable systems have to be

available to support the aircraft on the approach even in CAT III visibility conditions.

Performance based navigation is available; aircraft are equipped and can achieve required performance

criteria.

Analysis:

With a fully flexible and dynamic definition of the threshold (touchdown point), a marking or light

installation will need to be significantly different from current navigation aids. Splitting the runway circle in a

discrete number of segments provides threshold markers and gives visual guidance to the pilot.

Conventional navigation aids as ILS are not suitable anymore as they cannot support curved approaches, but

other ground based or space based navigation systems, like Microwave Landing Systems (MLS) and

Differential Global Positioning Systems (D-GPS) can provide a high number of different approach paths. The

highest flexibility is given by a satellite based system as it provides an unlimited number of approach and

departure routes.

Using these systems it has to be ensured that the required navigational accuracy is achieved.

A highly accurate reference should be available at the airport to provide correction signals for high accuracy

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of the navigation performance.

The coordinates of the touchdown point have to be available for the flight management system of aircraft to

calculate the approach or departure route horizontally and vertically. While today this point is clearly

defined with the threshold coordinates of the runway, this may be dynamically for the operation of the

Endless Runway. Arrival and departure routes will be described as a sequence of waypoints that are

dynamically calculated on the ground or on board the aircraft. Advanced FMSs may work without the need

for waypoints.

Augmented reality combines real and virtual elements to provide high situational awareness. As a basic form

of this technology are already available head-up displays (HUD). These can be used for additional on-board

guidance to present approach information to the pilot, as shown in the figure below.

With the further development of this type of technology, the combination of all kinds of navigational

support like synthetic terrain data, navigational waypoints, approach information, markings, and aircraft

information will contribute to the required situational awareness of the pilot.

4.4.6 Separation

REQ-ATM-11 Separation in approach

Departure routes should be strategically separated from approach routes.

Background literature:



The minimum separation has to be maintained at all stages of the flight. Current separation criteria will still

apply for the Endless Runway.

http://www.airlinereporter.com/wp-content/uploads/2012/03/hud.j

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Analysis:

Different approaches can be taken to separate departures from arrivals.

The following figure shows an approach, where a discrete number of points for departure or arrival are

defined. Different routes are available for each point and traffic streams are coordinated from and to the

runway.

TD 1

TD 3

TD 2

TO 1

The following table lists some of the advantages and disadvantages of separating traffic streams.

Advantages Disadvantages

Coordination of homogenous traffic Reduced flexibility in choosing the preferred route

Separated traffic streams

The second approach, presented below, present a fully flexible system where arrival and departure routes

are not separated and need to be coordinated vertically and time based.

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REQ-ATM-12 Separation on the runway

Separation minima shall be applied for aircraft on the runway to avoid collisions.




The runway is used simultaneously by more than one aircraft

The minimum separation has to be maintained at all stages of the flight. Current separation criteria will still

apply for the Endless Runway.

Analysis:

The curved nature of the circled runway and the smaller footprint of the airport provide new challenges for

aircraft separation.

Distances between aircraft on the runway with a circle radius of 1500 m (diameter of 3000 m equal to 1.68

NM) can be determined as follows (see also the figure below):

With 3 simultaneous operations a safety zone around the aircraft of 1.38NM is possible in optimal

conditions.

With 4 aircraft operating at the same time the safety zone reduces to around 1.1NM.

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Safety Zone1.38 NM

Safety Zone1.38 NM

Safety Zone1.38 NM

Runway Diameter 1.62 NM = 3000m

3 Aircraft

11

Safety Zone1.1 NM

Safety Zone1.1 NM

Safety Zone1.1 NM

Safety Zone1.1 NM Runway Diameter

1.62 NM = 3000m

4 Aircraft

Additional values are given below. The figures already indicate that separation values could be a limiting

factor for the size of the circle.

Radius 3 aircraft 4 aircraft

2000m 1.8NM 1.45NM

1000m 0.45NM 0.37NM

4.4.7 Situational awareness for air traffic controllers

REQ-ATM-13 Situational awareness for air traffic controllers

ATC shall have an adequate situational awareness of the operations around and on the airport with the

assistance of a suitable traffic monitoring system.




A high level of automation is available and a high level of information sharing is achieved taking into account

all participants in air traffic

In the same way as pilots are supported by augmented reality, tower operations will also benefit from the

combined presentation of real and synthetic generated information.

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Analysis:

Controllers will need an adequate situational awareness to manage the available runway resource, monitor

the aircraft movements and give instructions when needed. This is not only relevant for the tower

controllers but also for the approach controller. All systems are interconnected and can transfer information

and traffic situation.

Presentations of the actual traffic situation and new alerting mechanisms have to be integrated. The task of

the controller will significantly change and current tasks might be transferred to other stakeholders within

the airport.

Planning and prediction systems will calculate the traffic at the airport and support the controller in

managing the traffic flows rather than controlling individual aircraft.

4.4.8 Handle different meteorological conditions

REQ-ATM-14

REQ-ATM-15

Handle different meteorological conditions

The Endless Runway shall allow operations under low wind conditions.

The Endless Runway shall allow operations under high wind conditions.




It is assumed that for a trailing aircraft touching down at least 1 NM behind a leading aircraft, wake vortex

encounters will be mitigated.

It is assumed that the 1NM separation of the touchdown points together with the time difference of around

40 seconds of subsequent landings results in safely separated aircraft. The 40 seconds time separation is a

result of the composite separation (500 ft. + 1.25 NM) applied between subsequent aircraft approaching

inside the TMA.

Analysis:

When wind conditions are such that wind is at any touchdown point below the cross wind limit, aircraft are

sequenced so that touchdown points of subsequent landing aircraft are placed behind the leading aircraft. In

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this way the trailing aircraft stays outside the wake vortex of the leading aircraft, a shown in the following

figure.

Similarly, departing aircraft are placed at least 1NM behind the leading aircraft. In this way the trailing

aircraft stays outside the wake vortex of the leading aircraft.

When the wind conditions are such that wind is above the cross wind limit then aircraft are sequenced so

that touchdown points of subsequent landing aircraft are placed into the wind at opposite sides of the

runway. Subsequent aircraft land sequentially in a clockwise and counter-clockwise direction. The indicated

touchdown points can be moved downwind if they stay within the cross wind limit to allow for more

separation between subsequent aircraft in the rollout.

Similarly, aircraft are sequenced so that take-off points of subsequent departing aircraft are placed into the

wind at opposite sides of the runway. Subsequent aircraft depart sequentially in a clockwise and

counter-clockwise direction. The indicated lift-off points can be moved downwind if needed.

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The following figure presents the general concept of the runway operation in high wind conditions. Two

sectors are allowed for operation where crosswind is within the limits. Within these two zones touchdown

and lift-off take place.

The coloured strips represent the runway sections that are claimed for the operation. A safety buffer is

provided for opposite traffic operations.

55

56

57

58

6261

60

59

70 69 68 67 66 65 64

63

72 71

18

17

16

15

14

13

1211

10

98

76

5 4 3 12

19

20

21

22

23

24

25

26

27

28

2930

3132

3334 35 37 38 39

4041

42

4344

45

46

47

48

49

50

51

52

53

54

36

Segments not allowed for landing

Segments not allowed for takeoff

Wind Wind

Time from Time to 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72

08:00 08:01

08:01 08:02

08:02 08:03

08:03 08:04

08:04 08:05

08:05 08:06

08:06 08:07

08:07 08:08 only allowed for landing only allowed for takeoff only allowed for landing

… …

Segment

LH 1234 AF6666

IB 1111KL 3377

Dynamic safety buffer for

opposite landings

Dynamic zones for takeoff and landing

(crosswind in limits)

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REQ-ATM-16

REQ-ATM-17

Handle different meteorological conditions

The Endless Runway shall allow operations under all visibility conditions.

The Endless Runway shall be operative under snow, rain, and icing conditions.




-

Analysis:

Visibility

The Endless Runway shall be operated under all visibility conditions. This includes night operations, fog, and

during heavy rain. Based on the categories by ICAO, visibility is defined in terms of Runway Visual Range

(RVR) and decision height. A fully automated landing as described under CATIIIC could lead to additional

requirements in terms of navigation support, accuracy and aircraft capabilities.

Rain

Thanks to its curvature, standing water and aquaplaning will not be a problem for the runway. However,

sufficient drainage has to be provided to avoid standing water in the adjacent areas like entry and exit and

taxiway segments.

Snow/ice

Snow removal has to be possible. Typical procedures involve a number of staggered operating snow trucks

working on designated runways which are closed during this period. With the Endless Runway a full closure

of the circled runway would lead to a closed airport and no movement anymore. In addition a full snow

removal of the runway could take a long time.A solution is to apply dedicated snow removal equipment for

the banked runway that turn continuously on the runway. Aircraft can take-off and land behind the trucks on

those parts that have been cleared, taking into account a safety distance. An advantage is that only one type

of snow removal truck is necessary to clean the whole runway (where now mostly several different types are

necessary for one complete runway sweep).

A more static concept of separating the circle into segments would allow a partial closure of the runway. At

the closed regions snow removal can take place while other areas are still available for aircraft movements.

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Safety has to be ensured in this case. Depending on the curvature of the runway there could be a problem

for snow trucks at the outer edge of the runway, which is the steepest.

In combination with icy conditions sufficient adhesion is required to maintain the track in use.

4.4.9 Environmental aspects

0 Environmental aspects (avoid given areas)

Departure and arrival routes should be designed such that they will allow avoiding overflying given areas.




Airports with a circled runway will be located near populated areas.

Environmental aspects will be even more relevant in the future.

Analysis:

While REQ-ATM-06 is basically related to the cost effective definition of arrival and departure routes the

general concept can also be adapted to environmental constraints. With flexible approach routes, specific

areas can be avoided completely or only during times of the day. Noise abatement procedures can be

defined temporarily.

Use Cases 5.

This chapter provides some non-nominal situations that were found in the process of setting up the analysis in

chapter 4. Where possible, solutions are presented.

5.1 Emergency stop on the banked part of the runway

For runway configurations, where the bank angle reaches high values (e.g., 15°), aircraft emergency stops on

the banked part of the runway will lead to passengers experience discomfort.

A solution is to modify the landing gear configuration to level the fuselage, with independent left and right

landing gears height. The figure below shows that this option requires further research concerning the

decreased wingtip and engine clearance.

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If possible, rapid aircraft towing to the gate by airport ground vehicles seems to be the best solution.

5.2 Emergency landing

5.2.1 Malfunction of landing gear deployment

In case the landing gear cannot be deployed, the aircraft will have to perform a belly landing. First calculations

indicate that the aircraft will automatically move on the bank angle of the circular track to the position that fits

its speed and will reduce to stand still at the bottom of the bank. An alternative is a dedicated infrastructure

(such as a flat and straight portion of runway) that can be provided at the airport to comply with this

emergency situation.

5.2.2 Aircraft banking not possible before landing

The aircraft cannot roll due to a malfunction of the control surfaces. Therefore, it cannot be banked with the

angle required by the runway. Even though the aircraft could land and recover the right bank angle once on

ground, there is a risk of contact between the external wingtips and the runway. This is why a dedicated

infrastructure (such as a flat and straight portion of runway) may be needed.

5.2.3 Touchdown point not reached

For any reason (loss of automation and of cockpit display), the aircraft cannot reach precisely the touchdown

point and lands on the runway, but on another radius. As a consequence, aircraft speed and bank angle do not

match the ideal values of the runway track. The aircraft being not at equilibrium, a discomfort will be

experienced by passengers and the aircraft will spontaneously try to reach the proper circle, through a lateral

displacement.

As indicated in [3] landing outboard of the optimum speed circle is more comfortable and requires less control

displacement than landing inboard of that circle. Therefore, the pilot should try to aim the external area of the

runway.

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5.3 Different shapes

Earlier studies to circular runway tracks came with alternatives towards their shape, mainly to include

additional straights segments that will allow the take-off and landing to be performed on a short, straight inlet.

This section will provide an overview of the basic ideas for alternative shapes; for a full description, reference

[3] can be consulted.

Emergency strip

To allow the performance of emergency procedure, Bary describes a circle with a straight segment for

emergency procedures, see the figure below.

Bary’s straight chordal tracks

From the same designer as the straight emergency segment, a design is provided with straight chordal tracks

in the circle that allow the aircraft to take-off and land at the straight run and enter the circle only after

touchdown. This enables a take-off and landing without bank angle, see the three dotted areas in the figure

above.

Insets

Taking the idea of straight insets further, another design from Bary is the circle with several long straight

segments where the high speed part of the flight is performed. The insets can be constructed outside the circle

and, to safe space, inside the circle, see the figures below.

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The figures also show the track not completely a circle, but show small straight segments in the circle to allow

for a longer horizontal run or, which is the case in the figures above, to allow for the connection between the

straight segment and the circle.

The number of straight segments vary in between one and many, as indicated in the figure below.

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Conclusion 6.

This document contains the high level operational concept for operating the Endless Runway. Various

elements have been defined, based on the division between airport design, aircraft characteristics, and ATM

procedures. Each of the elements has been worked out in detail in a number of requirements, which all have

been further analysed.

It can be concluded that a circle of 3 km diameter will mostly fit the requirements for the size of the circle. The

total runway length is equivalent to about three conventional runways and can accommodate sufficient

movements for a seasonal airport or a large non-seasonal hub airport. Sufficient room is available inside the

circle to cater for gates, terminal buildings, and other necessary infrastructure, such as fire stations. All

non-essential infrastructures for aircraft handling will be positioned outside the circle.

The design of current-day aircraft gives points for consideration to operate the runway efficiently. The engines,

landing gear, and other equipment are not constructed for asymmetrical operations and the wingtip and

engine clearance on a banked runway needs further research. Future aircraft operating the Endless Runway

can be optimised in their design.

ATM procedures will require a high level of automation. Air traffic controllers will need assistance for

calculating the optimum take-off and touchdown point for each aircraft, taking other traffic and

meteorological conditions into account. Simultaneous aircraft movements for arrivals and departures, both in

clockwise and counter-clockwise directions may be possible, where more than one aircraft can occupy the

runway at the same time. The size of the runway has a strong influence on the separation in case of multiple

aircraft movements on the runway.

It can be concluded that no show stoppers for a further evaluation of the Endless Runway have been identified

in setting up the operational concept, but some points of concern are mentioned in the document and several

possible options need to be further studied.

References 7.

[1] ACARE (Advisory Council for Aeronautics Research in Europe), Aeronautics and Air Transport: Beyond

Vision 2020 (Towards 2050), Background Document, Issued: June 2010

[2] Hesselink, H.H., The Endless Runway – Work Plan for WP1, version 2.0, July 2012,

D1.1_WP1_Work_Plan.

[3] Loth, Sl, Dupeyrat, M. et.al., The Endless Runway – State of the Art, runway and airport design, ATM

procedures and aircraft, version 2.0, November 2011, D1.2_WP1_Background. [4] FAA RD-74-124, “Techniques for Determining Airport Airside Capacity and Delay (1976)”.

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Appendix A. Definition of gates

Parking areas for the aircraft can be defined with a series of standard stands considering the different aircraft

types. These are shown in the following picture.

Standard stand dimensions for different aircraft types

In order to make a better use of space, different types of contact stands can be merged. Nevertheless it must

be kept in mind that the distance from wingtip to any nearby object must not be surpassed. The following

table shows the mentioned distances considering the different aircraft types.

Stand type Aircraft code element Distance from wingtip to object

I

II E 7.5 m

III

IV D 7.5 m

V

VI

VII

VIII

A

B

C

4.5 m

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Stands are designed so that distances from wingtip to the stand side, for critical width aircraft, comply with the

rules. In order to save space, two stands can be merged as long as rules are not violated. The merging distance

will be the smaller of the two. The following pictures illustrate this.

Merged stands

Occasionally the following configuration of contact stands is adopted. The two apron drives that serve an

aircraft type E can be used to serve two mid-sized aeroplanes.

Flexible stands

Once different kinds of stands are described, the total number of stands required can be determined based on

the previous assumptions and the following equation:

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N= Number of stands

A= Aircraft Peak Design Hour

T= Time in stand

S= Separation between aircraft

Based on the information provided in the analysis, the following figures result from calculations:

Aircraft Peak

Design Hour

Number of

Stands

Total Peak Total 120 120+60=180

Int 60 60×2= 120

Nat 60 60×1=60

Peak Int Total 120 150+45=195

Int 75 75×2=150

Nat 45 45×1=45

Peak Nat Total 118 100+68=168

Int 50 50×2=100

Nat 68 68×1=68

The total number of stands required is composed of the required national flexible stands plus the international

flexible stands.

The number of non-flexible stands is the sum of the peak international stands during an international peak

period and the number of peak international that occurs during the national peak period:

NNF = 150 + 68 = 218 non-flexible stands

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The number of flexible stands is:

NFLEX = NNF – max(NPeaknat, NPeakint, NPeaktotal) =218 – max(168,195,180) = 23

The number of national and international stands now taking into account flexible stands is:

NF = NFNat + NFint = (68 – 23) + (150 – 23) = 45 + 127 = 172 stands

Considering the mentioned lengths per stand that appear under the assumptions section, the total airside

length needed is:

L = 45×45 + 65×127 = 10 280 m

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Appendix B. Automated People Movers

Automated People Movers (APM) transport passengers from public transportation stations and parking lots to

airport terminal buildings. APM systems can also connect the different terminal buildings of an airport. Their

main characteristics are:

Automatic, there is no need for drivers.

Supervised from a remote control station.

Reliability: over 99% of operation time.

Speed: reduction of circulation time between the external areas and the internal areas of the circle.

Up to date subsystems: ATP (Automatic Train Protection), ATO (Automatic Train Operation) and ATS

(Automatic Train Supervision).

More than one platform, depending on capacity.

Various systems have been developed depending on the distance between two points. Systems longer than

600 m use self-propelled vehicles. They consist of a rubber-tired self-propelled system. For shorter distances

and simple routes, cable-driven systems are used, which are cheaper than the former ones.

In the Endless Runway concept, the APM could make several stops outside of the circle, taking passengers that

arrive from railway stations, underground facilities, bus stations and parking areas to the main building.

People-mover system can also assist the distribution of passengers between different points in the terminal if

walking distances exceed 500 m.

As these systems can be very expensive, airport operators must determine their viability.

Documents

D1.3 oncept Description - endlessrunway-project.eu · D-GPS Differential Global Positioning System DLR Deutsches Zentrum für Luft- und Raumfahrt EASA European Aviation Safety Agency